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Flat-panel LCD TVs are all the rage, owing to their sleek, handsome designs, but it turns out they're not ideal for watching moving images. That's because the liquid crystal molecules in LCD panels move relatively slowly from one orientation to another. As a result, video or games played on an LCD can look smeared. You're actually better off with a CRT for those things, because the response of the phosphors to the electron beam in a CRT is nearly instantaneous. But continual improvements to the responsiveness of liquid crystal are helping speed up the on-screen action.

Liquid crystals have the special ability to twist light waves (
see the diagram
). A typical LCD uses a polarizing layer between the liquid crystal layer and the backlight to screen out all light waves except those oriented in a single plane. Another polarizing layer in front of the panel transmits only the light waves oriented in a different plane. In between, the liquid crystals either let the light pass through untwisted or twist the light so that the plane of the waves matches that of the second filter. This allows the light to be transmitted or blocked on demand.

An LCD panel may take an average of 16 to 25 milliseconds to change from white to black and back to white again. And these are the best-case measurements; changing from one shade of gray to another can take three to four times as long as that. This isn't a serious issue for images that don't move, such as word processing documents or spreadsheets, but a slow response time can be a problem when the LCD is used as a television.

One promising solution tricks a cell into changing more rapidly by giving it an initial charge greater than what it needs to achieve the correct shade of gray. This technology is often called overdrive or feed-forward. Taiwan-based AU Optronics has developed another solution, known as Intrinsic Property technology, that enables liquid crystals to move faster.

Another problem with LCDs is that image brightness and colors can change as your viewing angle changes. CRTs have a distinct advantage here, because they emit light from the surface of the screen, sending out light in all directions. Liquid crystal molecules are rod-shaped, however, so when they are aligned with each other, the image may look distorted if not viewed straight on. (Think of being able to see through window blinds only when you're at the correct angle.)

One solution, referred to as multidomain, is to divide each liquid crystal cell into multiple regions and build microscopic structures that cause the molecules to tilt in different directions. Although the individual areas still look different if you change the viewing angle, the average light from each cell has the correct brightness and hue from a wider range of viewing angles.